Tiny mite triggers domino effect in the high Andes
Pumas, condors and grasslands impacted after mange wipes out park's
vicun~as
Date:
March 8, 2022
Source:
University of California - Davis
Summary:
What happens when a disease disrupts a protected ecosystem so
forcefully that cascading consequences are felt by nearly all
wildlife and plants within it? A study examines how the mange
outbreak among vicun~as restructured tightly linked food-chain
interactions that were previously driven by pumas.
FULL STORY ==========================================================================
The idea of food chains and food webs in the animal kingdom is simple:
Remove a link or thread, and the system is broken. But nature is complex,
and it's not always clear how the absence of one species may impact
others.
========================================================================== Other times, the connection is devastatingly clear.
Argentina's wild vicun~as are close relatives of alpacas and llamas. For decades, vicun~as, pumas and condors have been intrinsically connected, sustaining the high Andes ecosystem of Argentina's San Guillermo National
Park: Vicun~as grazed the grass. Pumas preyed extensively upon the
vicun~a. And condors depended on the pumas' leftovers.
That is, until recent years, when one by one, each of these relationships unraveled across the landscape after a mange outbreak decimated the
park's vicun~a population in less than five years.
What happens when a disease disrupts a protected ecosystem so forcefully
that cascading consequences are felt by nearly all wildlife and plants
within it? A study published in the journalEcology Lettersexamines how
the mange outbreak among vicun~as restructured tightly linked food-chain interactions that were previously driven by pumas, also called mountain
lions or cougars.
========================================================================== Remote chances It also illustrates how even remote parks are not fully
safe from human impacts. A recent UC Davis study indicates the mange
outbreak stemmed from domestic llamas introduced to private lands outside
the park.
"This preserve is about as remote as you can get, with very little
human interaction, and yet it is still not safe from human activities
occurring hundreds of miles away," said co-leading author Justine Smith,
as assistant professor with the UC Davis Department of Wildlife, Fish and Conservation Biology. "Pathogens can take hold quickly, leaving animals
with little time to respond or adapt. We might see unintended consequences
that we should be preparing for when managing at-risk populations
of wildlife." Chain reactions Sarcoptic mange is a highly contagious
disease in which parasitic mites burrow under the skin, making it too
painful to move and forage. Many animals starve or become easy prey.
==========================================================================
When the study's authors began to see mange rapidly spread through the
park, they were already studying pumas and vicun~as there. They switched
gears to study the chain reaction of the disease outbreak in 2015.
They tracked condors, pumas and vicun~as with GPS devices and used a combination of on-the-ground vegetation surveys and remote sensing data
from satellites to analyze landscape changes. Researchers and field
technicians also collected data on vicun~a densities, mange prevalence
and puma hunting behavior.
Their findings show that introduced disease can cause rapid and
catastrophic changes to wildlife populations and their ecosystems.
"The changes to the landscape were really evident even as we were
collecting the data to confirm these patterns," said co-leading author
Julia Monk, a Ph.D.
candidate at Yale School of the Environment. "We went from seeing condors
daily to going months on end without encountering them, and the open
plains that were practically bare when I started working in the park
had exploded with vegetation by my next field season. " Tiny mite,
big changes Before the outbreak, pumas had been the biggest threat to
vicun~as, whose grazing strategy was designed around avoiding them. But
the tiny mite turned out to be the much bigger threat.
The study found that vicun~as plummeted from more than 17 individuals per square kilometer before the outbreak, to 1 per square kilometer by 2020.
Condors, which were the primary scavengers and abundant in the system, eventually left the park entirely when their food source disappeared.
The impact on pumas, the park's top carnivore, is less clear, as tracking collars were only operational through 2017. The authors know that at
least one puma they monitored starved to death, though puma sightings
remained common throughout the study. Anecdotally, the authors also
observed animals switching prey to smaller items, such as an instance
where a puma was hunting a tuco- tuco, a small rodent.
Range anxiety The changes among the animals also brought massive change
to the landscape.
Bare ground became covered in grasses over huge expanses visible from
space.
Vegetation increased up to 900% in areas where vicun~as preferentially
foraged to avoid becoming puma prey. There is some concern this growth
could spark a population explosion of European hares, although more
research is needed to verify those concerns.
"We don't really know how or if these systems will recover," Smith
said. "Will they return to the system we knew, or will a new balance
emerge from these dynamics? It's hard to predict." The scientists
say the study also highlights the importance of baseline monitoring,
basic research and supporting the capacity of scientists outside the
United States.
"Continuing to support our colleagues in Argentina who have worked for
decades to understand and protect this unique system will be vital for
tracing the continuing effects of the disease and for promoting the
ecosystem's recovery," Monk said.
Additional co-authoring institutions include Fundacio'n Rewilding
Argentina, INIBIOMA-CONICET in Argentina, University of Wisconsin-Madison, Smithsonian National Zoo and Conservation Biology Institute, Universidad Nacional de La Plata in Argentina, and UC Berkeley.
The research was supported by the National Geographic Society, Yale
University, UC Berkeley, CONICET and other conservation organizations.
========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Kat Kerlin. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Julia D. Monk, Justine A. Smith, Emiliano Donadi'o, Paula L. Perrig,
Ramiro D. Crego, Martin Fileni, Owen Bidder, Sergio A. Lambertucci,
Jonathan N. Pauli, Oswald J. Schmitz, Arthur D. Middleton. Cascading
effects of a disease outbreak in a remote protected area. Ecology
Letters, 2022; DOI: 10.1111/ele.13983 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220308102837.htm
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